In semiconductor processing, lift pins are used to lift and lower a semiconductor substrate onto a substrate support in a process chamber. Typically, a robotic arm transports the substrate into an upper portion of the process chamber where the substrate is deposited on lift pins that extend upwardly through the substrate support. The lift pins are then lowered into a lower portion of the process chamber to place the substrate on the substrate support. Afterwards, the robotic arm is withdrawn from the chamber.
After processing of the substrate, the lift pins are raised upward through bushings in the substrate support to lift the substrate off the substrate support by pushing up against the substrate. The robotic arm is then reinserted below the substrate to withdraw the processed substrate from the chamber. The inventors have discovered the conventional lift pin holders do not secure the lift pin well enough, thus allowing the lift pin to lean and rub against the bushings in the substrate support.
An additional problem with conventional lift pin assemblies arises when the lift pins attempt to lift the substrate off the substrate support and the movement of the lift pins is not a smooth continuous movement, but instead stuttered movement. The inventors have discovered that the stuttered movement is caused by debris falling into lift pin holders beneath the substrate support that support the lift pins. The stuttered movement would cause vibrations, which would cause particles generated from movement of the substrate to fall into the lift pin holder. The debris causes the lift pin to rub against the bushing as the lift pin is moved up or down. As a result, damage to the substrate may occur due to the stuttering movement of the lift pin. To address the stuttering issue, cleaning solutions have been used to clean the lift pin holders. However, because the cleaning does not address the underlying problem, debris falls into the lift pin holder again.
Therefore, the inventor has provided an improved lift pin holder and lift pin assemblies incorporating same.